Positive switch contact operating mechanism for underground switch

ABSTRACT

A positive switch contact operating mechanism for a vacuum interrupter unit of the type having a pair of contacts, one of which is moved relative to the other by a toggle or similar nondirect operating mechanism and wherein auxiliary lever structure assures opening of the contacts. The auxiliary lever structure is used to apply a direct force to the movable contact during opening of the switch to break a weld of the contacts which may have occurred. Alternatively, the lever structure is designed to render the toggle mechanism inoperative and preclude full movement of the operating arm from its nonoperated location to its operated location in the event that the lever structure is incapable of breaking the contact weld. This latter feature affords a visual indication of the position of the contacts and precludes any false impression that the contacts have been disengaged unless this, in fact, has occurred.

I United States Patent [1113562 454 [72] Inventor Philip G. Chance 2,838,636 6/1958 Schwager 200/l44.2(X)

Centralia, Mo. 2,862,075 1 H1958 Netzel ....200/67(PKS)(X) [21] Appl. No. 841,059 3,471,669 10/1969 Curtis 200/67(B)(X) [22] Filed July 11, 1969 Primary Examiner-Robert K. Schaefer patfamed 1971 Assistant Examiner-William J. Smith Asslgnee Chm Company Attorney-Schmidt, Johnson, Hovey & Williams Centralia, Mo. a corporation of Missouri [54] POSITIVE SWITCH CONTACT OPERATING ABSTRACT: positive switch contact operating mechanism MECHANISM FOR UNDERGROUND SWITCH for a vacuum interrupter unit of the type having a pair of con- 4 Claims 4 Drawing Figs. tacts, one of v/h1ch is moved relatlveto the other bv a toggle or similar nondirect operating mechanism and wherein auxiliary [52] US. Cl 200/67, lever Structure assures opening f the contacts The auxiliary 200/153 lever structure is used to apply a direct force to the movable [51] lnt.Cl ..H01h 21/00 Contact during Opening f the Switch to break a weld f the [50] Field of Search ..200/67(PKS), contacts which may have occurred. Alternatively the lever 67(3) 1441 153.7 structure is designed to render the toggle mechanism inoperative and preclude full movement of the o eratin arm from its [56] References CM nonoperated location to its operated loca ion in %he event that UNITED STATES PATENTS the lever structure is incapable of breaking the contact weld. 1,753,975 4/1930 Welsh 200/67(PKS) This latter feature affords a visual indication of the position of 2,426,880 9/1947 Jackson et a1. 200/67(PKS) the contacts and precludes any false impression that the con- 2,534,007 12/1950 Dietrich 200/67(PKS) tacts have been disengaged unless this, in fact, has occurred.

PATENTEU FEB 9:97: 3,5 2 454 INVENTOR 1 /7/7429 G. Char/0e ATTORNEYS POSITIVE SWITCH CONTACT OPERATING MECHANISM FOR UNDERGROUND SWITCH This invention relates to electrical switching apparatus and, more specifically, to a positive switch contact operating mechanism for a vacuum interrupter unit.

A vacuum interrupter unit of the type for which the present invention is particularly designed is disclosed in U.S. Pat. ap plication Ser. No. 698,291 entitled Encapsulated Switch Assembly For Underground Electrical Distribution Service, now U.S. Pat. No. 3,471,669. The disclosure of the foregoing application is incorporated herein by reference for a detailed showing and explanation of switching mechanism of the type for which the present invention is particularly designed.

Switching apparatus of the type described is particularly adapted for burial in an underground vault. To insure fast switching action, a toggle mechanism is employed to move one of two contacts relative to the other at a rate of speed to minimize arcing. The toggle mechanism is actuated by an an operating arm disposed outside of the switch housing. The vacuum switch contacts, by the nature of their design and environment, are very susceptible to joinder by becoming welded together especially when long periods of time elapse between periods of opening. The degree of welding depends upon several variables, e.g., the magnitude of the current, length of time the current flows, and contact pressure. Although a small degree of welding can be expected under normal operating conditions, severe welding is largely attributable to periods of abnormal current flow such as occurs during a high current short circuit or fault.

Because of the nature of the nondirect force that is applied by a toggle operating mechanism, full movement of the toggle operating arm from its nonoperated position to its operated position is possible even though welding of the contacts has precluded their disengagement. Thus, since the interior of the switch cannot be observed through the opaque housing thereof, full movement of the operating arm gives a workman the impression that the contacts have been disengaged when, in fact, this has not necessarily occurred. Obviously, this can result in an extremely hazardous situation.

It is, therefore, the primary object of this invention to provide a positive, fast-acting switch contact operating mechanism for a vacuum interrupter unit wherein full movement of the operating arm of the mechanism from its nonoperated location to its operated location is prevented unless the contacts move out of engagement, thereby avoiding any visual impression that the contacts have been disengaged unless this in fact has occurred. 1

Another very important object of this invention is to provide a positive switch contact operating mechanism for a vacuum interrupter unit wherein the switch will operate to break welding that occurs between the contacts, thereby permitting positive operation of the switch when joinder of the contacts as by welding thereof would otherwise preclude such operation.

As a corollary to the foregoing object, it is also an object of this invention to provide a positive switch contact operating mechanism for a vacuum interrupter unit wherein novel lever structure is emplaced in connection with the toggle members of the mechanism so as to assure that a high mechanical ad vantage is attained with the mechanism thus permitting a relatively strong weld between the switch contacts to be broken if necessary during actuation of the mechanism.

Other objects of the invention will be made clear or become apparent from the foregoing application and accompanying drawing, wherein:

FIG. 1 is a side elevational view of a vacuum interrupter unit and its associated operating mechanism, with parts thereof being broken away and in section and illustrating the contacts in their normally closed positions and the operating arm in its nonactuated location;

FIG. 2 is a side elevational view of the same apparatus as described in Fig. 1 but with the operating arm moved to its operated location to disengage the contacts;

FIG. 3 is a fragmentary, side elevational view of the apparatus of FIGS. 1 and 2 showing the contacts in welded engagement and illustrating how full movement of the operating arm from its nonoperated location to its operated location is prevented by novel lever structure associated with the operating mechanism; and

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 2.

Referring to the drawing, the numeral 10 designates generally the vacuum interrupter unit while contact operating mechanism 12 is joined thereto. The vacuum interrupter unit 10 includes a stationary contact 14 and a movable contact 16, both of which are disposed in an evacuated ceramic envelope (not shown); Appropriate sealing bellows (not shown) permit movement of the contact 16 relative to the contact 14 without breaking the vacuum within which the two contacts are disposed.

The operating mechanism 12 is mounted within a housing 18 connected to unit 10 and includes toggle mechanism 20 comprising a first link 22 pivotal on shaft 31 and a second link 24 keyed to and carried by the shaft. The links 22 and 24 are operatively interconnected by a yieldable member such as a pair of toggle springs 26. The link 22 is pivotally joined by a pin 28 (FIG. 4) to a switch operating rod 30 connected to contact 16 of switch 10. Link 22 is provided with an adjustable screw 32 disposed to engage a protrusion 34 on the housing 18 to act as a stop for the link 22, as illustrated in FIG. 2.

The link 24 is provided with an outwardly projecting, elongated rib 36 thereon. As previously noted, link 24 is pivotal about the shaft 31 relative to link 22. An external, manually actuatable operating member 40 is connected to shaft 31 for rotating the latter and link 24 joined thereto.

A movable .l or L-shaped lever element 42 is pivotally connected by pivot pin 33 at the uppermost end thereof and the lower part thereof is disposed in partial circumscribing relationship to shaft 31 and the toggle mechanism 12. Movable lever element 42 has a laterally extending, rigid boss portion 44 rotatable on pivot 33 (see FIG. 4). Boss portion 44 has a threaded, radially extending aperture therein spaced from the arm section of the lever 42 for receiving an adjusting screw 46 projecting from the tapped opening therefor. A laterally protruding ear 48 projecting from the lower leg of the element 42 is directly within the path of travel of the rib 36 on link 24.

An electrical connector 50 is mounted directly on the housing 18, and the end of the connector 50 projecting into the housing 18 provides a convenient means of physically and electrically connecting the operating rod 30 of contact 16 to the housing 18. This is accomplished through use of a flexible lead 52, the latter being illustrated in part by broken lines in FIG. 1. An electrical connector 54 is joined to the contact 14 at the end of the latter which is opposite the contact 16.

When it is necessary to disengage the contacts 14 and 16 in order to open the electrical circuit through the switch structure, the operating member 40 is moved from its nonoperated location as shown in FIG. 1 to its operated location as shown in FIG. 2. As the operating member 4 0 is moved clockwise, viewing FIG. 2, the link 24 which is keyed thereto will likewise move in a clockwise direction from a first overcenter position relative to the first link, as shown in FIG. 1, to a second overcenter position relative to the first link, as shown in FIG. 2. As the link 24 moves from its first overcenter position to its second overcenter position, the toggle spring 26 moves the link 22 counterclockwise from the position shown in FIG. 1 to the position shown in Fig. 2, thereby moving the contact 16 in a snap action fashion out of engagement with the contact 14. The laterally protruding ear 48 on the lever element 42 is engaged by the rib 36 of the link 24 as the latter moves from its first overcenter position to its second overcenter position. This, in turn, moves the lever 42 from the position shown in FIG. 1 to that shown in FIG. 2 wherein it is seen that the end of the lower leg of the lever 42 engages one wall of the housing 18 thereby forming a stop for the link 24 as the latter engages the ear 48. It is readily apparent that full movement of the operating member 40 from its nonoperated location to its operating location will proceed along an arcuate path of slightly greater than 90.

When welding of the contacts 14 and 16 has occurred, as illustrated schematically in FIG. 3, and the operating member 40 is moved from its nonoperating location, the link 42 engages the ear 48 of the lever 42, thereby moving the adjusting screw 46 into engagement with the first link 22. Continued movement of the operating member 40 causes a force to be applied to the link 22 thus serving to break the weld between the contacts and 16. If however, the extent welding between the contacts 14 and 16 is sufficiently great to prevent breaking thereof by the force applied through operating member 40 and lever element 42, full movement of the operating member from its nonoperated location to its operated location is prevented as clearly illustrated in FIG. 3. This prevents any false impression that the contacts 14 and 16 have been disengaged, and gives a positive indication of the position of the movable contact 16.

'The relatively high pulling force required to break the weld between the contacts is attributable to the mechanical advantage which results from the relatively short distance between the rotating axis of the second link 24 and the point of engagement of the latter with the laterally protruding ear 48 on the lever element 42, the relatively long distance between the pivot point of the lever element 42 and the point of engagement of the ear 48 with the link 24, and the relatively short distance between the pivot point of the lever element 42 and the point of engagement of the adjusting screw 46 with the link 22. Notwithstanding a tendency for the contacts 14 and 16 to stick or become welded, the lever structure in the nature of. element 42 either assures opening of the contacts of the vacuum switch or provides an easily observed indication of the open status of the internal contacts of the vacuum switch.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

I claim:

1. In a toggle switch unit provided with a pair of contacts, one of the contacts being movable relative to the other, toggle linkage for shifting the one contact out of and into engagement with the other contact including a first link pivotally joined to said one contact, a second link, a yieldable member interconnecting the first link and the second link for shifting the first link in a direction to move the one contact out of engagement with the other contact as the second link is moved from one overcenter position relative to the first link to a second overcenter position, and an operating member connected to said second link for shifting the latter between said first and second overcenter positions respectively as the operating member is shifted back and forth from corresponding nonoperated and operated locations thereof, the combination with said toggle linkage of mechanism for preventing full movement of the operating member from the nonoperated location into the operated location thereof unless said contacts move out of interengagement, said mechanism comprising:

a movable lever element having:

first means thereon located to engage the first link; and

second means thereon located to be engaged by the second link, and effect shifting of the element and thereby said one contact relative to the other contact as the second link is moved from said one overcenter position toward said second overcenter position.

2. The invention of claim 1, wherein the toggle switch is enclosed in a housing, said lever element being of generally L- shaped configuration, and wherein is provide structure pivotally mounting said element on the housing at a point ad- 7 jacent said first link at the uppermost end of the element and with a portion thereof in partial circumscribing relationship to said toggle mechanism.

3. The invention of claim 2, wherein said lever element is provided with a laterally extending, rigid arm on the uppermost extremity thereof, said arm being provided with a threaded opening therein and said first means comprising a threaded screw complementally received within said threaded opening and located to engage said first link.

4. The invention of claim 2, wherein said second means comprises a laterally protruding ear rigidly mounted on the lever element along the lower leg of the latter and within the path of travel of said second link. 

1. In a toggle switch unit provided with a pair of contacts, one of the contacts being movable relative to the other, toggle linkage for shifting the one contact out of and into engagement with the other contact including a first link pivotally joined to said one contact, a second link, a yieldable member interconnecting the first link and the second link for shifting the first link in a direction to move the one contact out of engagement with the other contact as the second link is moved from one overcenter position relative to the first link to a second overcenter position, and an operating member connected to said second link for shifting the latter between said first and second overcenter positions respectively as the operating member is shifted back and forth from corresponding nonoperated and operated locations thereof, the combination with said toggle linkage of mechanism for preventing full movement of the operating member from the nonoperated location into the operated location thereof unless said contacts move out of interengagement, said mechanism comprising: a movable lever element having: first means thereon located to engage the first link; and second means thereon located to be engaged by the second link, and effect shifting of the element and thereby said one contact relative to the other contact as the second link is moved from said one overcenter position toward said second overcenter position.
 2. The invention of claim 1, wherein the toggle switch is enclosed in a housing, said lever element being of generally L-shaped configuration, and wherein is provide structure pivotally mounting said element on the housing at a point adjacent said first link at the uppermost end of the element and with a portion thereof in partial circumscribing relationship to said toggle mechanism.
 3. The invention of claim 2, wherein said lever element is provided with a laterally extending, rigid arm on the uppermost extremity thereof, said arm being provided with a threaded opening therein and said first means comprising a threaded screw complementally received within said threaded opening and located to engage said first link.
 4. The invention of claim 2, wherein said second means comprises a laterally protruding ear rigidly mounted on the lever element along the lower leg of the latter and within the path of travel of said second link. 